I am the author of CryptoARM - most popular Russian software making/verifying digital signatures and making encrypted data.
I am the author for the following C++ libraries:
XSEC library - XSEC is a project allowing everyone to study very big part of information about Windows Access Control very quickly and by real life examples. Making access tokens with unlimited number of groups and privileges, adjust privileges, usage of AccessCheckByTypeResultListAndAuditAlarmByHandle function, parsing all data related to Access Control, store all to XML and many more.
ASN.1:2008 code and decoder - Free C++ ASN.1:2008 coder/decoder
CTjs (Official Web Site) - CTjs is a full set of classes necessary to work with any kind of Certificate Transparency log (V1 as from RFC6962, or V2 as from RFC6962-bis). In CTjs you could find all necessary validation/verification functions for all related data shipped with full-featured examples showning how to validate/verify. Also in scope of CTjs I made code showing example from RFC6962 item 2.1.3 on a real data from real Certificate Transparency log.
CAdESjs - CAdESjs is a specialized library making CAdES signatures by any level, up to LTA.
ByteStreamjs - ByteStreamjs is a set of classes manipulating with bytes and bits inside ArrayBuffer.
PAdESjs - (private repository at the moment, to be published soon). PAdESjs is a full-featured PDF parser and maker. With the library you could parse and make/modify any PDF file, with no restrictions, and could apply any PDF features, even from PDF 2.0 standard. Has PDF encryption/decryption functionality (password-based and certificate-based) and PDF signing functionality (all PAdES levels up to LTV).
pvutils - set of common routines for all repositories in PeculiarVenturies organization.